The present invention relates to headrests used in automobiles to prevent whiplash-type injuries, and more specifically to such a headrest that expands to offer better protection against such injuries.
Whiplash-type neck injuries are a common form of automotive vehicle injury, typically occurring when the vehicle is struck from the rear. A large number of whiplash injuries could be prevented or reduced in severity if the headrest were positioned closer to the head of the occupant at the time of the impact. Many vehicle occupants, however, fail to properly adjust the headrest so that the distance between the back of their head and the headrest is kept to a minimum.
Many systems have been proposed for moving the headrest forward toward the seat occupant""s head in reaction to a sensed or predicted rear impact. Such systems are referred to herein as active head restraint systems. Some known active systems utilize a pyrotechnically inflated airbag that expands forwardly out of the headrest or upwardly out of seatback between the headrest and the seat occupant""s head. (See, for example, U.S. Pat. Nos. 3,779,577 and 5,738,407.) Such pyrotechnically inflated systems have the drawback that once the airbag has deployed, resetting or repacking it is a complicated and expensive procedure that can only be performed by skilled automotive technicians. As a result, such pyrotechnic airbags can only practically be deployed by a crash sensor that detects vehicle accelerations caused by an impact. While many crash prediction systems utilizing a broad range of sensors (radar, lidar, ultrasonic, transponders, etc.) have been proposed, none of these systems are considered reliable enough at the present time to utilize them as a trigger for airbags, since the false-alarm rate may be significant and the consequences of a false alarm may be expensive.
The term xe2x80x9cresettablexe2x80x9d as used herein with regard to a deployable headrest refers to the quality whereby there is little or no permanent damage to the system when it deploys during an impact. After the event, it can be returned to the pre-deployment condition and be ready for another deployment without expensive repair. A resettable headrest may allow the use of a crash prediction system before the system has achieved a high degree of reliability. If a resettable headrest is deployed in response to a false alarm, the consequences will be mild, since the headrest can be returned to its pre-deployment condition quickly, simply and inexpensively.
Mechanically deployed headrests have been proposed which, by their nature, may be relatively inexpensive and simple to reset to a non-deployed or retracted condition after use. An example of a mechanically deployed headrest is disclosed in U.S. Pat. No. 5,694,320. As compared with inflatable systems, mechanical systems may be more difficult to control so that they are deployed in a safe manner, since they involve moving a solid object of relatively large mass toward the rear of the occupant""s head. If the headrest is still moving forward when it impacts the rearwardly moving head of the occupant, the kinetic energy of the impact will be increased, and so will the potential for injury.
Another safety concern with headrest design is the trade-off between the improved safety yielded by a larger, wide and taller headrest, and the decreased rearward visibility that such a larger headrest may cause. In general, a wider headrest would be advantageous during an accident since it will be more likely to effectively restrain the head of an occupant against whiplash injuries. If the headrest is narrow, the occupant""s head may glance off the side of a headrest if the seat occupant is not sitting in a centered position in the seat but is leaning to the left or right, or if the vehicle is involved in a rear angular impact.
The present invention provides an active head restraint system that overcomes the above-described limitations of both pyrotechnically inflatable and mechanical actuated headrests. In the disclosed embodiments of the invention, the head restraint system includes a collision prediction system for detecting objects approaching the vehicle from the rear, a pressure tank containing a quantity of pressurized air, a motor-driven compressor for maintaining a desired pressure in the tank, and an expandable headrest. The headrest comprises a base mounted to the seat back in conventionally known fashion, a pad connected to the base for movement between a rearward pre-deployment position and a forward deployed position, and at least one inflatable bladder located between the base and the pad. The bladder is connected with the pressure tank for inflation when activated by the collision prediction system.
When in the deflated condition, the bladder is substantially contained within the base, and the headrest has a relatively narrow pre-deployment configuration. When the bladder is inflated it expands to urge the pad forward, and simultaneously expands laterally outward beyond the pre-deployment perimeter of the base to enlarge the overall width of the headrest. The invention system thus provides a headrest that is relatively narrow when in the pre-deployment condition in order to minimize obstruction of the driver""s rearward vision and rear seat passengers, forward vision. When inflated, the headrest expands to a relatively wide configuration to provide improved head restraint during an accident.
The invention has the further benefit of being easily resettable due to the pneumatic inflation of the bladder. The motor driven air compressor used to pressurize the pressure tank is also usable for a multitude of other functions on the vehicle, such as a pneumatic suspension system.
In a first embodiment of the invention includes first and second laterally moveable wings which are slidingly mounted to the base and are urged outwardly in opposite directions by inflation of first and second bladders, thereby widening the headrest to decrease the likelihood that the occupant""s head will glance or roll off to the side the headrest after contact. The wings also provide a slightly concave front surface of the headrest that further help to prevent the occupant""s head from glancing or rolling to the side.
According to a second embodiment of the invention, a bladder is positioned to form a collar substantially surrounding the pad when in the inflated condition, thereby increasing both the width and height of the headrest and so providing better had restraint for seat occupants having different seated heights. The collar also provides a slightly concave front surface of the headrest that tends to prevent the seat occupants head from glancing or rolling to the side during a crash event.